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Fencing whales

Duration: 02:05

Dolphins and killer whales are descended from four-footed land-living air-breathing carnivorous mammals. In the sea they lost their limbs but not their taste for meat, or their teeth. Indeed, living in the ice-strewn waters of the Arctic is the narwhal, a member of the family that has grown one of its teeth to an extraordinary length. However, only the male narwhal grows the great tusk that can reach nine feet long. The ones with the smaller tusks are females. No one knows exactly what purpose the tusk serves but it may be used in courtship since males have, though very rarely, been filmed fencing with each other, their tusks poking out of the water.

Available since: Tue 11 Oct 2011

This clip is from

The Living Planet The Open Ocean

11/12 David Attenborough explores the ocean, which covers 70 per cent of the Earth's surface.

First broadcast: 29 Mar 1984

Image for The Open Ocean Not currently available on BBC iPlayer

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